Most old mythologies are keen to point out the weaknessess in the We - even if we are the sons of gods or centers of the universe... So Tolkien only follows a traditional path there by making Dunedain and elves having vices. The idea of the "chosen ones" being (needing or striving to be) perfect is later Christian addendum.
In the old world of mythologies you could be superior but still imperfect.
